Q: I drive a Mazda Miata that has an overdrive button on its shifter. Anytime I am going up a steep grade or coming down a hill, I disengage the overdrive to force the transmission into a lower gear. My friend says I am crazy and should just let the tranny do the work. But I don’t like the constant shifting up and down when going up a hill. Please answer. A cup of coffee is riding on this.

A: Enjoy that cup of coffee! Transmissions, smart as they may be, aren’t able (yet) to anticipate the road ahead or your plans for negotiating it. When driving in hilly country, it’s a great idea to drop a gear or two, or deselect overdrive, to avoid continual up and down shifting, and to provide engine braking on downgrades. Overdrive, in your case, is simply fourth gear, the uppermost gear. Newer Miatas with six-speed automatic transmissions have two overdrive gears, which can be easily toggled.

If it were a manual transmission, you wouldn’t think twice about choosing the gear you feel is best. I’ve found when passing on a two-lane road, it’s helpful to drop a gear or two prior to executing the pass. Skipping an awkward, six-to-four downshift as you pull out and mash the throttle provides an uninterrupted blast of power to get your business done.

Q: A recent column of yours got me thinking about a situation that happened a few years back. A female friend told me that a “car guy” friend told her it was safer, better and saved gas to put a car in park when waiting for a stop light. We are not talking about a 100-car railroad crossing where you could be stuck for minutes. We are talking about a normal, 10- or 30-second stop. In my understanding, the engine of an automatic transmission car engine runs at basically the same speed in park and in drive. So, I question the fuel savings. Moving from park to drive probably causes unnecessary wear on a transmission. And being in park in an emergency and trying to getting out of the way on short notice. What are your thoughts?

A: Oh boy. I agree with you that it’s awkward and unnecessary to place a transmission in park unless the delay will last more than a few minutes. It’s true there would be a tiny, insignificant reduction in fuel consumption as the engine is under slightly less load when in park than in drive. But staying in drive means less wear and tear on air conditioning hoses and fittings and other parts subjected to abrupt twisting as a shift is made. This goes for the transmission and driveline parts as well. Additionally, if you were in park and got bumped from behind because you didn’t get moving quickly enough, expensive transmission damage could occur. It’s also rude to give the person behind you a brief shot of backup lights just as they are preparing to accelerate!

— Bergholdt teaches automotive technology. Email questions to under-the-hood@earthlink.net.